TW200301294A - Electro-conductive composition, electro-conductive coating and method for producing the coating - Google Patents

Abstract

An electroconductive composition which comprises a particulate silver compound, a reducing agent and a dispersing medium. The particulate silver compound is silver oxide, silver carbonate, silver acetate or the like, the dispersing medium is water, an alcohol or the like, and the reducing agent is ethylene glycol, diethylene glycol or the like. The particulate silver compound preferably has an average particle diameter of 0.01 to 10 <mu>m. The electroconductive composition can be used for forming, without the use of a high temperature condition for film formation,an electroconductive coating which exhibits a low volume resistivity and high electroconductivity comparable to metallic silver and can provide an electric circuit having a satisfactorily fine line width with no increase in thickness in the formation of an circuit such as a flexible circuit board.

Description

说明 Description of the invention (the description of the invention should state: the technical field to which the invention belongs, the prior art, the content, the embodiments, and a brief explanation of the invention) [Technical Field to which the invention belongs] TECHNICAL FIELD The present invention relates to a conductive paste, The conductive composition used for conductive coatings, conductive adhesives, and the like, the method for forming the conductive coating using the conductive composition, and the conductive coating obtained by the forming method can fully improve the The conductivity of the obtained conductive film can be similar to that of metallic silver. [Background Art] A conventional conductive paste is represented by a silver paste, which is a thermoplastic resin, epoxy resin, epoxy resin, epoxy resin, epoxy resin, and the like mixed and mixed with layered silver particles. It is obtained by a binder, an organic solvent, a hardener, a catalyst and the like made of a thermosetting resin such as a resin and a polyester. This silver paste is widely used as a conductive adhesive, a conductive paint, and the like in various electronic devices, electronic parts, and electronic circuits. In addition, it is also used as a flexible printed circuit board for printing a silver paste on a plastic film of polyethylene terephthalate and the like by screen printing, and a printed circuit board for a keyboard and various switches. in. The method of using the silver paste is to coat the object with various coating devices and dry it at a hanging temperature or heat it to 150 ° C to form a conductive film. ^ Secondly, although the volume resistivity of the conductive film obtained according to this varies according to the film formation conditions, it is in the range of 1G-4 to nem. The volume resistivity of the father Li to metal silver is 1.6 × 1 —6Ω · cm is 10 ～ 100 times the value of the invention description, and it is always inferior to the conductivity of metallic silver. The reason why the conductivity of the conductive coating film composed of such a conventional silver paste is low is because of the following reasons, that is, only a part of the silver particles in the conductive coating film obtained from the silver paste are physically contacted and come into contact. There are few points; there is contact resistance at the contact point; a binder remains between the-part of the silver particles, and the binder hinders the direct contact of the silver particles. The silver paste is used as a method for improving the conductivity of the silver paste.

It is applied to an object and heated to the point where it is burned to remove the binder, and at the same time, the silver particles are melted and the wire particles are fused to form the same continuous metallic silver film 10. The volume resistivity of the conductive film thus obtained was 101Ω. The conductivity was close to the volume resistivity of metallic silver. However, this method has the disadvantage that it is limited to heat-resistant materials such as glass, ceramics, and enamel, which are resistant to high-temperature heating. Further, in the above-mentioned flexible circuit board, the 15-line width of a circuit formed on the circuit board is required to be reduced as much as possible. However, due to the silver

Particles have a layered shape with a particle size of 1 to 100 mm. Therefore, in principle, it is not possible to print a circuit with a line width smaller than the layered silver particle size. In addition, although it is required to reduce the wiring of the circuit, at the same time, it is required to have sufficient conduction of the knife. Therefore, the thickness of the circuit must be greatly increased according to the requirements. However, if the thickness of the circuit is increased, it is difficult to form a film, and the problem is that the flexibility of the circuit itself is greatly reduced. Accordingly, the object of the present invention is to provide a conductive film having a low volume resistivity and high conductivity, which is comparable to that of metallic silver, even if it does not comply with high temperature film forming conditions, and to obtain a flexible circuit board or the like When the circuit is sufficient, the conductive composition can reduce the line width of the circuit sufficiently without increasing its thickness. [Summary of the Invention] Disclosure of the Invention-In order to achieve the foregoing object, the conductive composition of the present invention is composed of a granular + silver compound and a reducing agent. This particulate silver compound is capable of making 帛. Silver oxide, silver carbonate, silver acetate, and the like. The average particle diameter of the particulate silver compound is 0.01 to 10 μm. The method for forming the conductive film of the present invention is a method of coating and heating a conductive composition. The conductive film of the present invention is obtained by the aforementioned forming method, and the silver particles are fused to each other. The conductive coating is obtained by coating the conductive composition and heating it at 150 to 20 (rc for 30 minutes). If the volume resistivity (Q · cm) of the V electrical coating is w, When the specific gravity is X, the following formula (1) is satisfied: WS — 1.72x10-6χχ + 2 · 3χ10-5… (1) Furthermore, “the conductive film is coated with the aforementioned conductive composition and is subjected to“ It is obtained by heating at 150 ~ 200 C for 30 minutes, and if the number of voids-number (number) that exists on the surface of the conductive composite film with a surface area of 10 pmx 10 pm or more is Y, and the heating temperature ( 1) is z, which satisfies the following formula (2): Υ <-46.08 · Zn + 10112 --- (2) The particulate silver compound is easily reduced to metallic silver particles by heating under the coexistence of a reducing agent. Moreover, the metallic silver particles precipitated by the heat of reaction during the reduction reaction are melted and fused with each other to form a highly conductive metallic silver coating. Therefore, the obtained conductive coating is comparable to metallic silver. The conductivity of the invention is illustrated in the drawing. The first diagram is a diagram of the conductivity of the conductive composition obtained from the conductive composition of the present invention. Scanning electron microscope photograph of the surface. Figure 2 is a scanning electron microscope photograph of the surface of a conductive film obtained from a conventional silver paste. Figure 3 is a volume resistivity of the conductive film in a specific example. The relationship between the specific gravity and the specific gravity. Figure 4 shows the relationship between the number of surface voids and the heating temperature of the conductive film in the specific example.

[Embodiment; J Preferred Embodiment of the Invention] The present invention will be described in detail below. The particulate silver compound used in the conductive composition of the present invention is a solid particulate compound having the property of being reduced to metal silver by heating in the presence of a reducing agent. Specific examples of the particulate silver compound include silver oxide, silver carbonate, and silver acetate. These may be used by mixing two or more kinds. The particulate silver compound can be used directly or classified by industrial producers, and can also be classified and used after pulverization. It is also possible to use one obtained by a liquid phase method or a gas phase method described later. The average particle diameter of the far-particle silver compound is in the range of 0.01 to 10 µm, and the reduction reaction conditions can be appropriately selected in accordance with, for example, the heating temperature, the reducing power of the reducing agent, and the like. In particular, when a particulate silver compound having an average particle diameter of 0.5 μm or less and described in the description of the invention is used, the reduction reaction speed is faster and more desirable. In addition, a particulate silver compound having an average particle diameter of 0.5 μm or less is produced by a reaction between a silver compound and another compound. For example, an alkaline aqueous solution such as sodium hydroxide can be dropped into an aqueous silver nitrate solution while stirring. Then, it is reacted to produce silver oxide by a liquid phase method. In this case, it is preferable to add a dispersion stabilizer to the solution to prevent aggregation of the precipitated particulate silver compound. In this liquid phase method, the particle diameter can be controlled by changing the silver compound concentration, the dispersion stabilizer concentration, and the like. In addition, in order to obtain particulate 10 silver compounds with fine particles having an average particle diameter of 0.1 μm or less, the gas phase method can be used to synthesize silver oxide by heating dental silver and oxygen in the gas phase and thermally oxidizing them. Since the reducing agent used in the present invention is for reducing the aforementioned particulate silver compound, the by-products after the reduction reaction are gas or highly volatile liquid and do not remain in the generated conductive film. Better. Specific examples of these 15 kinds of reducing agents include i, or a mixture of two or more kinds of ethylene glycol, diethylene glycol, diethylene glycol, ethylene glycol diacetate, and the like. The amount of the reducing agent used is preferably 20 mol or less relative to the particulate silver compound. Mol is less than 20 mol, and more preferably 0.5 to 10 mol. good. If the reaction efficiency or volatilization due to heating is taken into consideration, it is better to add more than equal moles. However, even if the amount exceeds 20 moles, the portion is in vain. A dispersion medium is used to disperse or dissolve the particulate silver compound and the reducing agent to obtain a liquid conductive composition. The dispersion medium uses water, 11 ^ 2UJ30i: 94 玖, the description of the alcohols such as methanol, ethanol, propanol, etc., isophorone, bis! Alcohol, triethylene glycol monobutylene bond, ethylene glycol Organic solvents such as monobutyl acetic acid. If the reducing agent is a liquid state in which the particulate silver compound is dispersed, the reducing agent may also serve as a dispersing medium. Examples of the reducing agent include ethylene glycol and 5-glycol. The selection of the type of the dispersion medium and its amount of use are different according to the particulate silver compound or film-forming conditions. For example, in the screen printing, the mesh thickness of the printing plate or the fineness of the printing pattern can be appropriately adjusted to optimize the Proper film formation. It may be added as a powder to disperse the particulate silver compounds having an average particle diameter of 1 or less, and it is preferable to prevent secondary aggregation of the particulate silver compounds. As this dispersant, propylcellulose and polytetrazine were used. The ratio is slightly larger, polyvinyl alcohol, and the like, and the usage amount thereof is 0 to 300 parts by weight based on 100 parts by weight of the particulate silver compound. The conductive composition of the present invention is one in which the aforementioned particulate silver compound and a reducing agent are dispersed and dissolved in a dispersion medium. Moreover, a dispersion | distribution back J may be added as needed. The average particle diameter of the particulate silver compound used here is not limited to those having a small particle diameter, and if it is in the range of 0.001 to 10 μm, there will be no particular problem, and even if the particle size is 1 μm or more, reduction The reaction can also proceed smoothly. In addition, the viscosity of the conductive composition varies depending on the film forming conditions, but it is preferably 30 to 300 poise, for example, when screen printing is performed. The method of using the X »Hi conductive composition, that is, the method for forming the conductive film of the present invention, is to apply the conductive composition to an object by an appropriate device and then heat it only. The heating temperature is based on the presence of a reducing agent. 12 2u03iC94 发明, the description of the invention is 140 ~ 160 ° C, and the heating time is 10 seconds ~ 120 minutes. In addition, of course, the surface of the object must be cleaned. The conductive coating film of the present invention thus obtained, the particulate silver compound, and the reduced and reduced metal silver particles are fused with each other to form a continuous gold thin film of silver. -Figure 1 is a scanning electron microscope photograph showing an example of the conductive film thus obtained. It is apparent from this photograph that those who constitute the continuous coating of metallic silver. Φ Therefore, the volume resistivity of the conductive film of the present invention shows a value of 3 to 108 × 6-6 Ω · cm, and is the same level as the volume resistivity of metallic silver. In addition, since the average particle diameter of the particulate silver compound is 0.001 to 10 μm, the line width of a circuit formed by printing the base material using the conductive composition can be made 10 μm or less, and because of the circuit itself, The conductivity is extremely high, so there is no need to increase the thickness of the circuit. Therefore, the circuit is easy to form and the circuit itself is highly flexible. "Lu Zaiyi's" is sufficient because the heating temperature used to form the conductive film is 14 ~ 160 c, so it can also be applied to objects with low heat resistance such as plastic films, and can form high conductive films At the same time, it will not cause _20 thermal degradation of the object. Furthermore, since the volume resistivity of the obtained conductive coating film is extremely low, sufficient conductivity can be obtained even if the thickness of the coating film is made extremely thin. The thickness of the film can be reduced by a portion which is inferior to the decrease in volume resistivity with respect to the conventional conductive paste. For example, when using a silver paste of 5x10-5Ω · cm, if 13 ^ 200301294 发明, the description of the invention requires a circuit specification with a thickness of 50μm, the volume resistivity of 3x10-% • cm can be achieved by the present invention, and the thickness can be made 3μm. In addition, since the surface on the substrate side of the obtained conductive film is a mirror surface rich in metallic silver gloss, the inside of the transparent substrate 5 such as glass or plastic film or the conductive film peeled from the substrate is The substrate-side surface can be used as a mirror with high reflectance and can be used in domestic and industrial applications. For example, it can be used as a mirror for a resonator of a laser device. Further, it is apparent that the following relationship is established regarding the conductive coating film obtained from the conductive composition of the present invention. That is, the volume resistivity and specific gravity of the conductive coating obtained by coating the above-mentioned conductive composition on a substrate such as a glass plate and heating it at 150 to 2 GG ° C for 3 G minutes are determined, and an attempt is made to determine the relationship between these. The volume resistivity of the conductive film. ㈣ is W, and its specific gravity is χ, it is obvious that the aforementioned formula (1) is satisfied. Therefore, by setting the specific gravity so that the volume resistivity of the obtained conductive film is smaller than the value of formula (i), a good conductive film can be obtained. · Observe and calculate the number of voids per unit area on the outermost surface of the conductive film obtained in the same way with a scanning electron microscope, and try to find the relationship between the number of voids and the heating temperature. When the number of voids (number) above the lungs with a surface area of 10 μηι × 10 μιη present on the outermost surface of the 性 20 film is Υ ′ and the heating temperature (.0 is ζ), the aforementioned formula (2) is obviously satisfied. From this relationship, it can be seen that, in order to form a good conductive film with few voids, the heating temperature can be appropriately controlled, and a high conductive film with a temperature of 14 ° C and a description of the invention can be obtained by heating at 180 ° C. The following shows a specific example of the conductivity with a small number of voids. (Example 1) -Silver was dissolved in 50 ml of ion-exchanged water, and it was interpreted that hydroxypropylcellulose (0.5 to 1 g of ice) was dissolved therein ( Dispersant); ^ 'Search and drop the 0.9M ~ 5ml 1M gold hydroxide aqueous solution in this aqueous solution and continue to G1G ~ 3G minutes, as a sublimation ㈣ floating solution. ：: Receiver' will be oxidized by methanol After silver wash 2 ~ 5 times and remove the remaining dagger Square fit () 6~ig of ethylene glycol (reducing agent) and create a paste made of a conductive composition of the present invention.

^ The conductive composition was patterned by screen printing to a thickness of 5 ~ 1 () on a poly-ethylene terephthalate film with a thickness of 15 ° C, and then was formed in a magic furnace at 15 ° C Heat for 30 minutes to 3 hours. 15

The volume resistivity of the pattern obtained is 3 to 6 x 10, .cm. When the surface is observed by a Sumida electron microscope, as shown in Figure IX, the silver particles reduced and precipitated from silver oxide are fused and bonded. (Example 2) For comparison, a commercially available silver paste (brand name "FA — 353" manufactured by Fujikura Kasei Co., Ltd.) was used, and the silver paste was applied to polyparaphenylene diene with a thickness of 20 0.1 mm by screen printing. After a 5 to 10 μm 2 pattern was formed on the ethylene formate film, it was heated in an oven at 15 ° C. for 30 minutes. The volume resistivity of the obtained pattern was 4 × 10-5 Ω · cm. When scanning the surface with a scanning electron microscope, the silver layers were only contact bears. When using other commercially available silver paste (manufactured by the Asahi Chemical Research Institute) and forming a pattern in the same manner as described in the invention, the volume resistance was 15 The rate is 3 × ω—5Ω · ⑽. When the surface is observed with a scanning electron microscope, as shown in the photograph of the scanning cat electron microscope in Figure 2, the silver layers are only contact-like bears. (Example 3) ) On the glass substrate made of constant weight, apply the conductive composition of the aforementioned Example 1 with a thickness of 5 to 10 angstroms, and heat it in an oven at 15 (rtx3G ", fine. C X 30 knives' When measuring the volume resistivity and specific gravity of the obtained conductive film and determining the relationship, The result is shown in the graph shown in Fig. 3. When the regression equation is obtained from the graph, the above-mentioned formula (1) can be obtained. The conductive film prepared in the same manner was observed with a scanning electron microscope. When the number of voids existing on the surface is calculated and the relationship between the number of voids and the heating temperature is obtained, the result shown in Fig. 4 can be obtained. When the regression equation is obtained from this graph, the aforementioned formula ( 2). (Example 4) Using 100 parts by weight of silver oxide as the particulate silver compound and using 75 parts by weight of ethylene glycol as the reducing agent, and changing the average particle diameter of the silver oxide to form a conductive film, The volume resistivity was measured. Furthermore, the presence or absence of fusion between the silver particles was observed by a scanning electron microscope. A 0.1-mm-thick polyethylene terephthalate film was used on the substrate and printed on the screen. A pattern having a thickness of 5 to 10 was formed and heated at 150 ° C for 30 minutes to 3 hours. The silver oxide having an average particle size of 0.01 μm was prepared by a gas phase method, and the average particle size was 10 to 玖. ~ One is made by liquid phase method, average Those having a particle size of 15 μl were used by classifying commercially available products. The results are shown in Table 1.

A silver oxide having an average particle diameter of 0.25 mm was used as the kind of particulate silver compound and the type and combination of odor reducing agents to form a conductive film, and its volume resistivity was measured. In addition, the silver particles were observed by a concealed electron microscope, and fusion was performed. 75 weight parts of the total weight of the reducing agent was mixed with 100 weight parts of the silver oxide. A thickness of 0.1 mm was used on the substrate. A polyethylene terephthalate film was formed on the film by screen printing to a thickness of 5 to 10 mm, and heated at 150 ° C for 30 minutes to 3 hours. The results are shown in Table 2. 17 发明, Invention Description

Types of test number reducing agents: ethylene glycol and diethylene glycol —-------- Glycol Diacetate Purpose Volume resistivity (Ω · cm) Is there any melting between silver particles? # ^ --— —_ The result of clothing shows that even if the type and combination of reducing agents are changed,

The volume resistivity is also A., Ω · Cm, which can form a conductive coating without any problems in practical use. ^ 5 (Example 6) types and combinations to form a conductive coating. Also, by The scanning electron microscope was used to change the granular silver compound film, and the volume resistivity was measured to observe the fusion between the silver particles. The reducing agent was ethylene glycol and was blended with respect to the total weight of the particulate 10 silver compound in parts by weight. 75 parts by weight. Use a thickness (Umm of polyethylene terephthalate film 'on the substrate and form a pattern with a thickness of 5 to 10 by screen printing: heating at 150 ° C for 30 minutes to 3 Hours. 'Results are shown in Tables 3 and 4. 18 15 UJ30i294 玖, Description of Invention Table 3 Test No. 14 15 16 17 18 Granular silver compound silver carbonate silver carbonate silver carbonate silver acetate average particle size (μπι) 0.1 1.5 5 5 10 Volume resistivity 4x 10'6 1 7.5χ 1〇 ~ 6) 8x 10 ~ 6 &gt; 6.5χ 10〇 6 8x 1〇'6 (Ω · cm) 7x 1〇 ~ 6 (lx 10 -5 C 1 · 2χ 10-5 (lx 10 ~ 5 1 3 · 4χ 10.5 Table 4 Test 5 Formula Number 19 20 21 22 23 24 25 Particle silver compound silver oxide silver oxide silver oxide silver carbonate silver oxide silver oxide silver oxide average particle size (μπι) 0.25 0.25 0.25 5 0.35 0.25 0.25 Blending ratio (wt %) 50 70 50 60 50 33 50 Particulate silver compound silver carbonate silver carbonate silver acetate silver acetate silver acetate silver carbonate silver carbonate average particle diameter 0.35 5 5 5 5 0.35 5 Blending ratio (wt%) 50 30 50 40 50 33 25 granular silver compound—silver acetate average particle diameter of silver acetate (um) one — 5 5 blending ratio (wt%) one — 34 25 volume resistivity (Ω · cm) 4x 10'6 1 6.7x 10 '6 7x 1〇-6 1 8.3χ 1〇 ~ 6 6.2χ 1〇 ~ 6 1 8.5χ 10 ~ 6 8χ 10-6 1 1.2χ1 (Γ5 5.4χ 10'6 1 9.1χ 10 ~ 6 4.2χ 1 〇-6 1 7χ 10 ~ 6 7 · 9χ 1〇-6 1 1.lx 10 -5 Whether the silver particles are fused or not With or without the presence or absence The results in Tables 3 and 4 show that even with silver oxide , Silver carbonate, silver acetate, or a combination thereof, and the volume resistivity is also in the range of 10-6 Ω · cm, which can form a conductive film without problems in practical use. As described above, if the conductive composition of the present invention is used, a '__30i294' can be obtained. Explanation of the Invention-A conductive film having extremely high conductivity. In addition, since the formation of the conductive film can be sufficiently performed by heating at a relatively low temperature, a base material such as a touch-resistant plastic can be used. Furthermore, when the conductive composition is shaped &amp; the circuit, the line width of the circuit can be sufficiently reduced without increasing its thickness. . 5 Industrial applications · The conductive composition of the present invention can be used as a conductive paste, a conductive coating, a conductive adhesive, and the like. It can also be used for circuit formation of printed wiring boards such as flexible printed circuit boards. Moreover, the conductive film Lu can also be used as a reflective film with high reflectance. 10 [Brief description of the formula] Fig. 1 is a scanning electron microscope photograph of the surface of a conductive film obtained from the conductive composition of the present invention. Fig. 2 is a scanning electron microscope photograph of the surface of a conductive film obtained from a conventional silver paste. 15 Figure 3 is a graph showing the relationship between the volume resistivity and the specific gravity of the conductive film in a specific example. • Figure 4 is a graph showing the relationship between the number of surface voids of the conductive film and the heating temperature in the specific example. [Symbol table of the main components of the diagram] (None) 20

Claims (1)

^ 200301294 The scope of patent application is that it contains particulate silver compounds and g g t, ί =} |} 1 · A conductive composition. 2. The conductive composition according to item 1 of the scope of the patent application, wherein the pre-polar silver compound is one of silver oxide, silver carbonate, and silver acetate, or more than two or five. 3. The conductive composition according to item 1 of the scope of patent application, wherein the average particle diameter of the aforementioned granular silver compound is from 0.01 to 10 μm. 4. The conductive composition according to item 1 of the application, wherein the reducing agent is one of ethylene glycol, diethylene glycol, diethylene glycol, ethylene glycol diacetate, or 2 or more. 5. · A method for forming a conductive film, which is a method of coating and heating a conductive composition according to any one of claims 1 to 4 of the scope of patent application. 6. A conductive film, which is obtained by coating and heating a conductive composition according to any one of claims 1-4, and the silver particles &gt; are fused to each other. 7 · —A kind of conductive film, which is obtained by coating and heating the conductive composition as described in any one of the claims No. 丨 to No. 4 in the application, and the volume resistivity is 3.0 × 10-6 to 8.0x10- 6Ω · cm. 8 · —A kind of conductive film, which is obtained by coating the conductive composition as described in any one of claims 1-4 in the scope of application for patent and heating it at 150 ~ 20 (rc for 30 minutes, and if The volume resistivity (Ω · em) of the conductive film is W, and its specific gravity is X, which satisfies the following formula (1), namely: WS —1.72x10-6χ × + 2 · 3χ1〇-, · ⑴. 9 · A conductive film, which is coated with a conductive composition according to any of the patent application scope No. 丨 to 4 21 2uJ301294, any of the patent application scope, and obtained by heating for 15 to 2001: 30 minutes, and If the number of voids (100 nm) with a surface area of 100 μm or more existing on the outermost surface of the conductive film is 100 μm and the heating temperature (° C) is Z, the following formula (2) is satisfied, That is: γ &lt; — 46.08 · z + 1〇112 ... ⑺. twenty two